I mean, it's a way to set priorities. Even it turns out not to be an iron clad guarantee, having taken that pledge means when people end up taking too much time

I mean, it's a way to set priorities. Even it turns out not to be an iron clad guarantee, having taken that pledge means when people end up taking too much time fixing bugs, it's already consensus that that's not acceptable, and it'll presumably be much easier to make the case to allocate resources to address it.